Repeated rows and repeated people are different problems. A person can attend two sessions, so removing duplicates by Email alone would delete a legitimate booking. Choose Email and Session together when a duplicate means the same person booked the same session twice.
Select the whole table, then open Data > Data cleanup > Remove duplicates. Check Data has header row when the selection includes headings. Choose the comparison columns and confirm. Sheets keeps the first occurrence and reports how many duplicate rows it removed and how many unique rows remain. The comparison ignores letter case, so an uppercase email can still match its lowercase copy.
Trim whitespace is a separate cleanup command. It removes spaces at the ends and reduces repeated ordinary spaces between words. Review the intended key before deleting records; deduplication cannot tell whether two same-name people are the same person.